Here is a sample of your request using all members of a group. Just put this line in the group leader's init field. I believe that if you change the "group this" to "thislist" and have this line of code in the "on Activation" field of a trigger, it will apply the eventhandler to any unit that satifies the trigger condition (e.g. "West Present" will apply the EH to all west units in the trigger area).
{_x addeventhandler ["killed", {_this exec "yourscript.sqs"}]} forEach units group this
Hope that this helps!
Wadmann